Current drill chucks generally consist of a drill body, jaws, a nut, a bearing and a coat, wherein the drill body is connected with a transmission shaft of a power source, three jaws are respectively mounted within three equally distributed slanting holes in the drill body, the jaws have threads thereon which form thread transmission with the nut, and when the coat connected with the nut is rotated, the jaws can move along the slanting holes with respect to the drill body, thereby clamping or loosening a tool handle.
For the drill chucks of the above structure, as the threads between the jaws and the nut produce great contact stress under working load, which renders great friction from relative sliding, the clamping force for clamping a tool handle created by the thread transmission between the nut and the jaws is not large enough, which results in that the jaws cannot firmly clamp the tool handle under the operation condition of large load and vibration, and thus there exists a hidden trouble of looseness.
To improve the clamping property of the drill chucks and avoid loosening of the jaws during operation, there exist multiple known ratchet wheel pawl self-locking mechanisms, which aim to prevent loosening of the jaws.
U.S. Pat. No. 5,829,761 discloses a drill chuck comprising a self-locking mechanism (a locking system), wherein the basic member of this self-locking mechanism is a spring-steel member (a spring-steel entrainment element), and the spring-steel member is formed at the end with pawls which can engage with ratchets arranged along the outer circumference of the drill body, so that the spring-steel member can only rotate in one direction with respect to the drill body, thereby forming self-locking.
U.S. Pat. No. 6,390,481 discloses a drill chuck, comprising a chuck body, multiple jaws, a sleeve driving the multiple jaws, and a bearing element, wherein a first race of the bearing defines one ratchet wheel, and a second race defines pawls which can engage with the ratchet wheel. The mutual engagement between the pawls and the ratchet wheel can form self-locking.
However, the inventors of the present invention note that in the above drill chucks, adopting the common ratchet wheel pawl self-locking mechanism will bring trouble to the overall design of the drill chucks, including, but not limited to, that using the common ratchet wheel pawl self-locking mechanism will render the structural design of the drill chuck unreasonable or render it unable to be used in the design of the drill chucks.